Read/write device for a hard-disk memory system, and corresponding manufacturing process

ABSTRACT

Various embodiments of the present disclosure provide a read/write device for a hard-disk memory system. The read/write device includes a fixed structure; a membrane region including a first and a second membrane, which are constrained to the fixed structure, and a central portion, interposed between the first and second membranes; a first and a second piezoelectric actuator, mechanically coupled, respectively, to the first and second membranes; and a read/write head, which is fixed to the central portion of the membrane region. The first and second piezoelectric actuators can be controlled so as to cause corresponding deformations of the first and second membranes, said deformations of the first and second membranes causing corresponding movements of the read/write head with respect to the fixed structure.

BACKGROUND Technical Field

The present disclosure relates to a read/write device for a hard-diskmemory system; furthermore, the present disclosure refers to thecorresponding manufacturing process.

Description of the Related Art

As is known, numerous memory systems of the so-called hard-disk type areavailable today, each of which includes a respective disk, whichfunctions as memory medium and in which the data can be read and writtenand a respective read/write system.

FIG. 1 shows a memory system 1 that includes a disk 2 of magneticmaterial, in which data tracks are present (one of which is representedand designated by 4). As illustrated in FIGS. 2 and 3, each track 4comprises a plurality of magnetic portions 6; furthermore, the state(orientation) of magnetization of each magnetic portion 6, and moreprecisely of a corresponding number of Weiss domains, can be associatedwith a corresponding logic value, and therefore with the value of acorresponding bit.

Reading/writing of the magnetic portions 6 of the tracks 4 is carriedout by a read/write head 8, the position of which with respect to thedisk 2 is varied via an actuation system 10, which typically includes anarm 12 (FIG. 1) and a slider 14 (FIG. 2).

In particular, assuming an orthogonal reference system XYZ fixed withrespect to the memory system 1, the arm 12 can turn, under the action ofa corresponding electric motor (not shown), about a first axis H1parallel to the axis Z, which is laterally staggered with respect to thedisk 2 and traverses a first end of the arm 12. The slider 14 (not shownin FIG. 1) is constrained to a second end of the arm 12 so as to be ableto turn, under the action of a corresponding electric actuator (notshown), about a second axis H2, which is parallel to the axis Z andtraverses the second end of the arm 12.

As illustrated in FIG. 2, the read/write head 8 is fixed to the slider14 and overlies the disk 2, at a distance therefrom. As illustrated inFIG. 3, where it may be observed that the disk 2 has a cylindricalshape, and if we refer to the surface S_(data) to denote the base of thecylindrical shape facing the read/write head 8, the read/write head 8 isspaced from the surface S_(data) by a distance d that is typically 1 nm.The gap between the read/write head 8 and the surface S_(data) isoccupied by air.

In use, the disk 2 is kept in rotation about a third axis H3 by acorresponding electric motor (not shown); the third axis H3 is parallelto the axis Z and coincides with the axis of the disk 2. Furthermore,the actuation system 10 moves the read/write head 8, to a firstapproximation in a way parallel to the surface S_(data), i.e., parallelto the plane XY.

In particular, the actuation system 10 moves the read/write head 8 so asto arrange it each time over a desired track 4. Furthermore, given ageneric position in which the read/write head 8 is arranged above atrack 4, and considering the small sizes of the read/write head 8, therotation of the underlying disk 2 causes, as may be seen in FIGS. 2 and3, a part of track 4, arranged underneath the read/write head 8, toslide with respect to the latter approximately along a direction D, witha speed in the order of 130 km/h. Furthermore, as shown in FIG. 3, themagnetic portions 6 of the track 4 have a width L (measured in adirection perpendicular to the direction D) that is typically less than50 nm. Once again with reference to FIGS. 2 and 3, an orthogonalreference system X′Y′Z′ is represented therein, which is fixed to theslider 14 and is orientated so that the axis Z′ is parallel to the axisZ, and moreover so that the aforementioned direction D of sliding of thetrack 4 with respect to the read/write head 8 is parallel to the axisX′.

Further examples of coupling between the arm 12, the slider 14, and theread/write head 8 are illustrated in FIGS. 4A and 4B, which highlight,respectively: the movement of rotation (designated by R1) of the arm 12about the first axis H1; and the movement of rotation (designated by R2)of the slider 14 about the second axis H2.

As shown in FIG. 4C, solutions are known in which the actuation system10 is such as to enable, in addition to the aforementioned rotations, atranslation (designated by T in FIG. 4C) of the read/write head 8 withrespect to the slider 14. In particular, with reference to FIGS. 2 and3, id is desirable to translate the read/write head 8 with respect tothe slider 14 in a direction parallel to the axis Y′. In this way, thepositioning of the read/write head 8 with respect to the tracks 4 can beparticularly precise, with consequent possibility of increasing thedensity of the tracks 4 of the disk 2, and therefore increasing thedata-storage capacity.

An example of solution of the type shown in FIG. 4C is described in thepaper by J. Liu, et al. Thermal actuator for accurate positioningread/write element in hard disk drive, Microsystem Technologies,Springer-Verlag (published online on Jun. 28, 2012); in this document, athermal actuator is described, which enables translation of theread/write head with respect to the slider. Unfortunately, the degree ofpossible translation along the axis Y′ that can be obtained using theaforementioned thermal actuator is somewhat limited (less than 10 nm).

BRIEF SUMMARY

The present disclosure provides an actuator device that will enabletranslation of the read/write head with respect to the slider and thatwill overcome at least in part the drawbacks of the prior art.

According to the present disclosure, a read/write device and acorresponding manufacturing method are provided.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a better understanding of the present disclosure, variousembodiments thereof will now be described, purely by way of non-limitingexample, with reference to the attached drawings, wherein:

FIG. 1 schematically shows a perspective view of a hard-disk memorysystem;

FIG. 2 schematically shows an enlarged perspective view of a portion ofthe memory system shown in FIG. 1;

FIG. 3 schematically shows an enlarged perspective view, with partsremoved, of a portion of the memory system shown in FIG. 1;

FIGS. 4A-4C schematically show perspective views of actuation systemsfor hard-disk memory systems;

FIGS. 5, 6, and 9 schematically show cross-sectional views of anactuator device, taken along the lines of section V-V, VI-VI, and IX-IX,respectively, shown in FIG. 7;

FIG. 7 schematically shows a top view, with portions removed, of theactuator device shown in FIGS. 5, 6 and 9;

FIG. 8 schematically shows a perspective view, with portions removed, ofa part of the actuator device shown in FIGS. 5, 6, 7 and 9;

FIGS. 10-15 schematically show cross-sectional views of a semiconductorwafer, during successive steps of a manufacturing process (FIGS. 11-14refer to a same first plane of section, whereas FIGS. 10 and 15 refer toa different second plane of section);

FIG. 16 schematically shows a perspective view, with portions removed,of the wafer shown in FIG. 15;

FIG. 17 schematically shows a cross-sectional view of the wafer shown inFIG. 15, after a subsequent step of the manufacturing process, and in athird plane of section, different from the first and the second planesof section;

FIG. 18 schematically shows a perspective view, with portions removed,of the wafer shown in FIG. 17;

FIG. 19 schematically shows a top view, with portions removed, of thewafer shown in FIGS. 17 and 18;

FIG. 20 schematically shows a cross-sectional view of the wafer shown inFIG. 17, after a subsequent step of the manufacturing process, thesection being taken in the third plane of section;

FIG. 21 schematically shows a perspective view, with portions removed,of a part of the wafer shown in FIG. 20;

FIG. 22 schematically shows a perspective view, with portions removed,of the part of wafer shown in FIG. 21, after a subsequent step of themanufacturing process;

FIG. 23 schematically shows a top view, with parts removed, of the wafershown in FIG. 22;

FIG. 24 schematically shows a cross-sectional view of the wafer shown inFIG. 23, taken along a line of section XXIV-XXIV shown in FIG. 23;

FIG. 25 schematically shows a perspective view of a portion of a furtherwafer;

FIG. 26 schematically shows a cross-sectional view of an assembly formedby two wafers;

FIGS. 27 and 28 schematically show two different cross-sectional viewsof the wafer assembly shown in FIG. 26, after execution of a furtherstep of the manufacturing process;

FIG. 29 schematically shows a same section of the wafer assembly shownin FIG. 28, after execution of a further step of the manufacturingprocess;

FIGS. 30 and 31 schematically show cross-sectional views of a furtherwafer assembly, during execution of successive steps of themanufacturing process;

FIG. 32 schematically shows a top view, with portions removed, of theassembly shown in FIG. 31;

FIGS. 33-38 schematically show perspective views of sections of theassembly shown in FIG. 32;

FIG. 39 schematically shows a perspective view of a read/write device,in use;

FIGS. 40 and 41 schematically show top views of variants of theread/write device;

FIG. 42 schematically shows a perspective view, with portions, of awafer;

FIGS. 43 and 44 schematically show cross-sectional views of an assemblyincluding the wafer of FIG. 42, during successive steps of amanufacturing process;

FIG. 45 schematically shows a perspective view of a device obtained bysingulation of the assembly shown in FIGS. 43 and 44;

FIG. 46 shows a side view of the device shown in FIG. 45, after asubsequent step of the manufacturing process;

FIG. 47 schematically shows a perspective view, with portions removed,of a part of the device shown in FIG. 46; and

FIG. 48 schematically shows a perspective view of a read/write device,in use.

DETAILED DESCRIPTION

FIG. 5 shows an actuator device 20 of a MEMS type, which comprises asemiconductor body 201, which is, for example, of silicon, has anapproximately parallelepipedal shape and is delimited at the top and atthe bottom by a first and a second surface S₂, S₁, respectively.Moreover, FIG. 5 shows an orthogonal reference system ABC such that thefirst and second surfaces S₁, S₂ are parallel to the plane AB.

The semiconductor body 201 has a thickness, for example, comprisedbetween 50 μm and 500 μm. Moreover, present within the semiconductorbody 201 are a first and a second cavity 22, 24, which have, forexample, parallelepipedal shapes, that are approximately the same andwith sides parallel or perpendicular to the plane AB.

In greater detail, the first and second cavities 22, 24 extend to a samedepth. In particular, if we denote, respectively, by P₁ and P₂ the topwalls of the first and second cavities 22, 24, respectively, these areparallel to the plane AB and spaced by a distance w_(f) (for example, ofapproximately 3 μm) from the first surface S₁. Said distance w_(f)represents the thickness of a front portion of the semiconductor body201 that is interposed between the first surface S₁ and the first andsecond cavities 22, 24 and is referred to in what follows as themembrane region M. The membrane region M therefore comprises a first anda second membrane M′, M″ (which are shown in FIG. 5), formed by theportions of semiconductor body 201 that extend over the first and secondcavities 22, 24, respectively.

In even greater detail, in top view (FIG. 7), the first and secondcavities 22, 24 have elongated shapes along the axis A and are alignedalong the axis A. Extending between the first and second cavities 22, 24is a part of semiconductor body 201, referred to in what follows as theintermediate semiconductor region 23. Also the intermediatesemiconductor region 23 is overlaid by the membrane region M.

A rear layer 206, of dielectric material is present underneath thesemiconductor body 201.

As may be seen in FIG. 6, moreover extending in the semiconductor body201, starting from the first surface S₁, is a circular trench TH, whichextends at a distance from the second surface S₂. In particular, thecircular trench TH is laterally staggered with respect to the first andsecond cavities 22, 24; furthermore, the circular trench TH laterallydelimits a cylindrical portion VH of semiconductor body 201. Thecircular trench TH may have a depth that is approximately 80% of thedistance between the first and second surfaces S₁, S₂.

The actuator device 20 also comprises a first and a second inner coatingregion 25A, 25B, which are of thermal oxide and coat, respectively, thewalls of the first cavity 22 and the walls of the second cavity 24.Furthermore, the actuator device 20 comprises a first outer coatingregion 25C, which is of thermal oxide and extends on the first surfaceS₁, as well as within the circular trench TH. The first and second innercoating regions 25A, 25B and the first outer coating region 25C have athickness, for example, comprised between 0.2 μm and 3 μm.

If we denote by P₁′ and Pa′ the bottom walls of the first and secondcavities 22, 24, respectively, the parts of the first inner coatingregion 25A that coat the top wall P₁ and the bottom wall P₁′,respectively, of the first cavity 22 will be referred to in what followsas first and second parts 25A′, 25A″ (FIG. 5) of the first inner coatingregion 25A. Likewise, the parts of the second inner coating region 25Bthat coat the top wall P₂ and the bottom wall P₂′, respectively, of thesecond cavity 24 will be referred to in what follows as first and secondparts 25B′, 25B″ (FIG. 5) of the second inner coating region 25B.

The actuator device 20 further comprises a second outer coating region27, which is of TEOS oxide and extends on the first outer coating region25C. The second outer coating region 27 has a thickness, for example,comprised between 0.1 μm and 1 μm.

The first and second outer coating regions 25C, 27 overlie, among otherthings, the membrane region M.

The actuator device 20 further comprises an actuation system 35, whichincludes a conductive region 19 (for example, of a metal, such asplatinum), which extends over portions of the first and second outercoating regions 25C, 27 that overlie the membrane region M. In addition,the conductive region 19 partially overlies, at a distance, both thefirst and the second cavities 22, 24, as well as the intermediatesemiconductor region 23.

The actuation system 35 further comprises a first and a secondpiezoelectric region 32, 34, which are of piezoelectric material (forexample, PZT) and have, to a first approximation, a planar shape,arranged parallel to the plane AB.

In greater detail, the first and second piezoelectric regions 32, 34 areapproximately the same, have a rectangular shape, elongated along theaxis A, and are arranged on the conductive region 19, in direct contacttherewith.

In even greater detail, the first and second piezoelectric regions 32,34 are arranged symmetrically with respect to a plane of symmetry SH,which is parallel to the plane BC. Also the first and second cavities22, 24 are arranged symmetrically with respect to the plane of symmetrySH. Moreover, the first and second piezoelectric regions 32, 34 overlieat a distance the first and second cavities 22, 24, respectively.

In practice, the conductive region 19 functions as bottom electroderegion, which is shared by the first and second piezoelectric regions32, 34.

The actuation system 35 further comprises a first and a second topelectrode region 36, 38, which are of a metal material (for example,platinum, or TiW or Ru) or iridium oxide, are the same as one anotherand overlie, in direct contact, the first and second piezoelectricregions 32, 34, respectively.

The actuator device 20 further comprises a third outer coating region28, which is of dielectric material (for example, an oxide used inchemical vapor deposition, such as TEOS or USG) and is arranged on theparts of the second outer coating region 27 that are left exposed by theconductive region 19, as well as on the part of conductive region 19left exposed by the first and second piezoelectric regions 32, 34.

The actuator device 20 further comprises conductive paths CP and afourth outer coating region 29.

The conductive paths CP are interposed between the third and fourthouter coating regions 28, 29 and contact, the first or the second topelectrode region 36, 38, alternatively. In particular, visible in FIGS.5 and 6 is a path CP′ (not shown in FIG. 7), which contacts part of thesecond top electrode region 38 and moreover extends in part through thefirst, second, and third outer coating regions 25C, 27, 28 so as tocontact the cylindrical portion VH of the semiconductor body 201, whichwill function as TSV.

The fourth outer coating region 29 is of dielectric material (forexample, silicon nitride) and extends over the exposed portions of thethird outer coating region 28, as well as over the paths CP, CP′ andover the exposed portions of the first and second top electrode regions36, 38.

As may be seen in FIGS. 7 and 8, also present in the actuator device 20are a first and a second trench T1, T2. In this regard, for simplicityof representation, the conductive region 19, the conductive paths CP,the first and second top electrode regions 36, 38, the third and fourthouter coating regions 28, 29, the rear layer 206 and the circular trenchTH are not shown in FIG. 8; moreover, for simplicity, in FIG. 8 it hasbeen assumed that the first and second inner coating regions 25A, 25Bhave an infinitesimal thickness, and are therefore not illustrated.

The first and second trenches T1, T2 have the same shape, being(approximately) shaped like parallelepipeds that extend in a directionparallel to the axis A, symmetrically with respect to the first andsecond piezoelectric regions 32, 34. The first and second piezoelectricregions 32, 34 are therefore interposed between the first and secondtrenches T1, T2.

In greater detail, each of the first and second trenches T1, T2 overliesboth the first and the second cavities 22, 24 and extends through thefirst, second, third and fourth outer coating regions 25C, 27, 28, 29,as well as through the membrane region M and the first parts 25A′, 25B′of the first and second inner coating regions 25A, 25B. Consequently,each of the first and second trenches T1, T2 communicates or isfluidically coupled with the underlying first and second cavities 22, 24and is open both at the top and at the bottom.

In even greater detail, each one of the first and second trenches T1, T2is delimited by a respective inner side wall, parallel to the plane ACand facing the first and second piezoelectric regions 32, 34, and by arespective outer side wall, parallel to the plane AC and facingoutwards; in particular, the outer side walls of the first and secondtrenches T1, T2 are denoted, respectively, by PL_(T1) and PL_(T2) inFIGS. 7 and 8. Likewise, each of the first and second cavities 22, 24 isdelimited by a respective first side wall PL_(a), parallel to the planeAC and arranged, in top view, on a side of the assembly formed by thefirst and second piezoelectric regions 32, 34, and by a respectivesecond side wall PL_(b), parallel to the plane AC and arranged, in topview, on another side of the ensemble formed by the first and secondpiezoelectric regions 32, 34. This having been said, as may be seen inFIG. 7, and without this implying any loss of generality, the outer sidewall PL_(T1) of the first trench T1 is approximately coplanar with thefirst side walls PL_(a) of the first and second cavities 22, 24;furthermore, the outer side wall PL_(T2) of the second trench T2 isapproximately coplanar with the second side walls PL_(b) of the firstand second cavities 22, 24.

As may be seen in FIGS. 7-9, the actuator device 20 further comprises adeformable region 240, of a silicone polymer.

In detail, the deformable region 240 has approximately the shape of aparallelepiped and extends adjacent to the outer side wall PL_(T1) ofthe first trench T1. In particular, part of the outer side wall PL_(T1)of the first trench T1 is formed by the deformable region 240.

In greater detail, if we denote by P_(ext) a side surface that delimitsthe semiconductor body 201, is parallel to the plane AC, and is suchthat the first trench T1 is interposed between the side surface P_(ext)and the first and second piezoelectric regions 32, 34, the deformableregion 240 faces out over the side surface P_(ext). In other words, thedeformable region 240 is interposed between the side surface P_(ext)that laterally delimits the semiconductor body 201 and the outer sidewall PL_(T1) of the first trench T1. The deformable region 240 istherefore laterally staggered with respect to the first trench T1, andtherefore is laterally staggered also with respect to the membraneregion M.

As may be seen in FIG. 9 (where, to facilitate understanding,represented by a dotted line are the volumes of the first and secondcavities 22, 24, in actual fact not visible in this section), thedeformable region 240 extends vertically through the first, second,third and fourth outer coating regions 25C, 27, 28, 29, as well asthrough a part of the semiconductor body 201.

In greater detail, the deformable region 240 has a symmetrical shapewith respect to the plane of symmetry SH. In addition, the deformableregion 240 has a height such that it penetrates into the semiconductorbody 201 up to a depth at least equal to the depth of extension of thesurfaces (denoted by S_(xx)) that delimit at the top the second parts25A″, 25B″ of the first and second inner coating regions 25A, 25B (whichare also represented in FIG. 9, even though in actual fact they are notvisible in this view, with the sole purpose of facilitatingunderstanding). Without this implying any loss of generality, in FIGS. 8and 9 the deformable region 240 penetrates into the semiconductor body201 up to a depth equal to the depth of extension of the bottom wallsP₁′ and P₂′ of the first and second cavities 22, 24. Furthermore, in adirection parallel to the axis C, the portion of deformable region 240that extends through the semiconductor body 201 has a height, forexample, of approximately 5 μm.

All this having been said, the actuator device 20 is formed, togetherwith a plurality of other actuator devices that are identical to it (notshown), starting from a first wafer 200 (FIG. 10) and following themanufacturing process that is described hereinafter described withreference to just the actuator device 20, except where otherwisespecified.

As illustrated in FIG. 10, initially provided is the first wafer 200,which includes the semiconductor body 201, is delimited at the top andat the bottom by a top surface S_(top) and a bottom surface S_(bot),respectively, which are designed to form the first and second surfacesS₁, S₂, respectively.

In addition, present within the semiconductor body 201 are the first andsecond cavities 22, 24, which are of a buried type, may be formed in aper se known manner and are overlaid by a front semiconductor region202, which has the aforementioned thickness w_(f) and is designed toform the membrane region M.

For instance, formation of the first and second cavities 22, 24 may beobtained as taught in the European patent EP 1577656. In this case,albeit not illustrated, for each one of the first and second cavities22, 24, deep trenches are initially formed, separated by columns ofsemiconductor material; next, an epitaxial growth is carried out in adeoxidizing environment so as to grow, over the columns of semiconductormaterial, an epitaxial layer that closes the trenches at the top,trapping the gas present therein. Then, a thermal annealing treatment iscarried out that causes a migration of the atoms of semiconductormaterial and formation of a buried cavity that is empty (except forpossible residual gases), which delimits on the bottom, a correspondingsuspended region, i.e., a corresponding membrane, forming part of thefront semiconductor region 202.

Next, as shown in FIG. 11, a chemical etch of a dry type is carried outin order to selectively remove portions of semiconductor body 201 andform the circular trench TH, which extends from the top surface S_(top).

Next, as shown in FIG. 12, a further etch is carried out in order toform a first and a second hole 30, 31, which extend between the topsurface S_(top) and the first and second cavities 22, 24, respectively,and have a cylindrical shape with a diameter that is, for example,approximately 2 μm.

Then, as shown in FIG. 13, a process of thermal oxidation is carriedout, which causes formation of a first dielectric layer 205, which has athickness, for example, of approximately 1 μm and coats the walls of thefirst and second cavities 22, 24, without filling them. Moreover, thefirst dielectric layer 205 coats the side walls of the first and secondholes 30, 31, without occluding them completely; in particular, theportions of first dielectric layer 205 that coat the side walls of thefirst and second holes 30, 31 laterally delimit, respectively, a firstand a second opening A1, A2, which communicate with the first and secondcavities 22, 24, respectively. In addition, the first dielectric layer205 fills the circular trench TH completely and extends so as to coatthe top surface Sto_(p).

The first dielectric layer 205 is designed to form the first and secondinner coating regions 25A, 25B and the first outer coating region 25C.

Once again with reference to FIG. 13, for simplicity of representationthe reduction in thickness of the front semiconductor region 202 causedby the aforementioned thermal oxidation is neglected. Moreover, thermaloxidation also causes formation of the rear layer 206, arranged on thebottom surface S_(bot) of the semiconductor body 201.

Next, as shown in FIG. 14, a deposition of TEOS oxide is carried out soas to form, on the first dielectric layer 205, a second dielectric layer207. In particular, if we denote by S₂₀₅ the top surface of the firstdielectric layer 205, the second dielectric layer 207 extends on thesurface S₂₀₅. Moreover, the second dielectric layer 207 closes the firstand second openings A1, A2 at the top without, to a first approximation,penetrating into them.

In greater detail, albeit not shown, formation of the second dielectriclayer 207 may envisage deposition of an initial layer (not represented)of TEOS having a thickness, for example, of 1 μm, a subsequent processof densification, and a further subsequent process ofchemical-mechanical polishing (CMP) to reduce the thickness of theinitial layer down to 0.5 μm; the residual portion of initial layerforms, as a result, the second dielectric layer 207.

The second dielectric layer 207 is designed to form the second outercoating region 27.

Next, as shown in FIGS. 15 and 16, in a per se known manner theactuation system 35 is formed over the second dielectric layer 207.

In particular, the conductive region 19 of platinum is formed, whichoverlies (at a distance) the first and second cavities 22, 24 and theintermediate semiconductor region 23, which is interposed between thefirst and second cavities 22, 24 and extends underneath the frontsemiconductor region 202. In addition, formed over the conductive region19 are the first and second piezoelectric regions 32, 34 and the firstand second top electrode regions 36, 38. Furthermore, a first and asecond coating layer 208, 209 are formed, which are, for example, of USGand silicon nitride, respectively, and are designed to form the thirdand fourth outer coating regions 28, 29, respectively. Once again in aper se known manner, the conductive paths CP, CP′ are formed between thefirst and second coating layers 208, 209.

For simplicity of representation, FIG. 16 (as also the subsequent FIG.18) shows just the semiconductor body 201, the first and seconddielectric layers 205, 207, and the first and second piezoelectricregions 32, 34, as well as two imaginary lines 122, 124, which represent(approximately) the projections of the first and second cavities 22, 24,respectively, in a plane where it is assumed that the bases of the firstand second piezoelectric regions 32, 34 lie; furthermore further contourlines 130, 131 are shown in FIG. 16, which represent the projections ofthe first and second holes 30, 31, respectively, in the aforementionedplane.

Next, as shown in FIG. 17 (where to facilitate understanding theprofiles of the first and second cavities 22, 24 are represented by adotted line, which in themselves are not visible in this section) and 18(to which the same simplifications as those of FIG. 16 apply), asuccession of chemical etches, for example of a dry type, is carried outin order to form a recess 215. Once again with reference to FIG. 17, theprofiles are represented therein by a dotted line (in actual fact, notvisible) of parts (denoted, respectively, by 205A′ and 205A″) of thefirst dielectric layer 205 that coat the top wall P₁ and the bottom wallP₁′, respectively, of the first cavity 22 and are designed to form thefirst and second parts 25A′, 25A″, respectively, of the first innercoating region 25A. Furthermore, the profiles are represented by adotted line (in actual fact, not visible) of parts (designated,respectively, by 205B′ and 205B″) of the first dielectric layer 205 thatcoat the top wall P₂ and the bottom wall P₂′, respectively, of thesecond cavity 22 and are designed to form the first and second parts25B′, 25B″, respectively, of the second inner coating region 25B.

In practice, vertically aligned portions of the first and seconddielectric layers 205, 207 and of the first and second coating layers208, 209 are selectively removed, in addition to a part of thesemiconductor body 201 adjacent to the front semiconductor region 202,so as to form the aforementioned recess 215, which extends underneaththe top surface S_(top) for a depth, for example, of approximately 5 μmand is designed to house the deformable region 240.

In detail, the recess 215 has approximately a parallelepipedal shape andextends through the first and second dielectric layers 205, 207 and thefirst and second coating layers 208, 209, as well as through part of thesemiconductor body 201. In addition, the recess 215 is arrangedsymmetrically with respect to the plane of symmetry SH.

In greater detail, if we denote by P₃ the bottom wall of the recess 215,this extends to a depth at least equal to the depth of extension of thesurfaces (which are denoted by S_(kk) and are designed to form theaforementioned surfaces S_(xx)) that delimit the parts 205A″ and 205B″of the first dielectric layer 205 at the top. Without this implying anyloss of generality, in FIG. 17 the wall P₃ is coplanar with the bottomwalls P₁′ and P₂′ of the first and second cavities 22, 24.

As may be seen in FIG. 19 (where for simplicity of representation justthe semiconductor body 201, the first and second piezoelectric regions32, 34, the first and second cavities 22, 24, and the recess 215 areshown), the recess 215 is laterally staggered along the axis B withrespect to the first and second piezoelectric regions 32, 34, in a firstdirection. Without this implying any loss of generality, also the firstand second holes 30, 31 are laterally staggered along the axis B withrespect to the first and second piezoelectric regions 32, 34, but in adirection opposite to the aforementioned first direction.

In even greater detail, if we denote by P₄ the side wall of the recess215 arranged parallel to the plane AC and close to the first and secondcavities 22, 24, to a first approximation, the wall P₄ is coplanar withthe first side walls PL_(a) of the first and second cavities 22, 24.

Next, as illustrated in FIGS. 20 and 21, formed within the recess 215 isa preliminary deformable region 240′, which is of a silicone polymer, isdesigned to form the deformable region 240, and fills the recess 215.For instance, formation of the preliminary deformable region 240′ may beobtained via a process of spinning and subsequent patterning, so thatthe preliminary deformable region 240′ will face out over a surface S₂₀₉that delimits the second coating layer 209 at the top.

Next, as shown in FIG. 22 (to which the same simplifications of FIG. 8apply), 23 and 24, a new succession of etches is carried out, forexample of a dry type, so as to form the first and second trenches T1,T2 and, therefore, render the first and second cavities 22, 24accessible, since, as explained previously, the first and secondtrenches T1, T2 function as ducts in so far as they are open downwards.

In particular, formation of the first and second trenches T1, T2 entailsremoval of peripheral parts of the front semiconductor region 202, sothat the remaining central part of the front semiconductor region 202forms the membrane region M. Formation of the first and second trenchesT1, T2 moreover entails removal of parts of the first and seconddielectric layers 205, 207 and of the first and second coating layers208, 209.

Following upon formation of the first and second trenches T1, T2, thefirst dielectric layer 205 is divided into the first and second innercoating regions 25A, 25B, as well as the first outer coating region 25C.

Next, as shown in FIG. 26, the first wafer 200 is mechanically coupledto a second wafer 299 (shown in FIG. 25), which is, for example, of anAlTiC alloy and includes a supporting body 300, in which housingcavities 302 are formed (one of which is visible in FIG. 25).

The supporting body 300 of the second wafer 299 is delimited by a basesurface 304, onto which the housing cavities 302 face out, each of whichcorresponds to a respective actuator device 20 of the first wafer 200.Consequently, in what follows, reference is made to a single actuatordevice 20 and to the corresponding housing cavity 302, except whereotherwise specified.

In detail, the first wafer 200 is flipped over and is fixed to thesecond wafer 299. More in particular, the actuator device 20 is flippedover and is fixed to the supporting body 300 so that the membrane regionM, and therefore the first and second cavities 22, 24 and the first andsecond piezoelectric regions 32, 34 will overlie the housing cavity 302.

Without this implying any loss of generality, as may be seen in FIG. 32,coupling is such that the outer side walls PL_(T1), PL_(T2) of the firstand second trenches T1, T2 are approximately coplanar with underlyingside walls of the housing cavity 302, which, moreover has an elongatedshape parallel to the axis A so that the first and second cavities 22,24, and therefore also the first and second piezoelectric regions 32,34, are entirely suspended over the housing cavity 302. Instead, in topview, the preliminary deformable region 240′ is laterally staggered withrespect to the housing cavity 302. Coupling is obtained byinterposition, between the second coating layer 209 and the base surface304, of a gluing region 305, for example, of a benzocyclobutene-basedresin. The preliminary deformable region 240′ comes into abutmentagainst an underlying part of the gluing region 305, since it islaterally staggered with respect to the housing cavity 302.

Next, as shown in FIG. 27, an operation of grinding andchemical-mechanical polishing is carried out so as to remove the rearlayer 206 and reduce the thickness of the semiconductor body 201. Inparticular, as may be seen in FIG. 28, grinding and polishing lead totwo successive reductions of the thickness of the semiconductor body 201(for example, down to 30 μm and then down to 25 μm) so as to expose thecircular trench TH and part of the first outer coating region 25Ccontained therein. Following upon the above operations, thesemiconductor body 201 is delimited at the top by a new bottom surfaceS_(bot)′.

Next, as shown in FIG. 29, the contact regions are formed. For instance,FIG. 29 shows the contact region CP″, arranged above the bottom surfaceS_(bot)′, in direct contact with the cylindrical portion VH.

Moreover, a layer 211 is formed over the new bottom surface S_(bot)′,referred to in what follows as coupling layer 211. The coupling layer211 is of a USG or TEOS oxide, deposited by chemical vapor deposition,and has a thickness, for example, of 1 μm. The contact region CP″extends through the coupling layer 211.

Then, as shown in FIG. 30, a top structure 400 is formed over the firstwafer 200, and in particular on the coupling layer 211.

In particular, the top structure 400 is obtained by chemical vapordeposition of alumina (aluminum oxide). In addition, the top structure400 comprises a plurality of read/write heads 404 of a per se knowntype, i.e., portions at least in part of alumina, each of which includesa respective conductive coil that can be controlled electronically by anexternal driving circuit so as to be traversed by electrical signals (inparticular, currents) that are able to write the magnetic tracks 4 orthat are indicative of the data stored in the magnetic tracks 4. A coil,designated by 405, is schematically shown in FIGS. 30 and 43.

Furthermore, the top structure 400 comprises a respective main body 402,to which the read/write heads 404 are fixed. The main body 402 iswithout read/write coils.

The main body 402 of the top structure 400 is formed on the couplinglayer 211; furthermore, each read/write head 404 extends over acorresponding housing cavity 302, and therefore over a correspondingactuator device 20. In what follows, the description will be limited toa single read/write head 404. In addition, in what follows, the mainsurface of the top structure 400 facing the side opposite to the secondwafer 200 is referred to as the surface to be etched S_(etch).

Albeit not shown, corresponding contacts are formed on the top structure400, which are electrically connected to the coils 405 of the read/writeheads 404 and enable electrical coupling of the latter to the outsideworld, and in particular to the respective driving circuits.

Next, as shown in FIGS. 31 and 32, a further succession of etches iscarried out, for example of a dry type, starting from the surface to beetched Seta, so as to selectively remove portions of the main body 402that surround the read/write head 404 laterally, as well as underlyingportions of the coupling layer 211 and underlying portions of thesemiconductor body 201, until portions of the first and second innercoating regions 25A, 25B that coat, respectively, the bottom walls P₁′and P₂′ of the first and second cavities 22, 24 (i.e., theaforementioned second parts 25A″, 25B″ of the first and second innercoating regions 25A, 25B) are etched. Etching, however, does not involveportions of the first and second inner coating regions 25A, 25B thatcoat, respectively, the top walls P₁ and P₂ of the first and secondcavities 22, 24 (i.e., the aforementioned first parts 25A′, 25B′ of thefirst and second inner coating regions 25A, 25B). To a firstapproximation, it may be assumed that the operations of etching stop ata depth equal to the depth where the second parts 25A″, 25B″ of thefirst and second inner coating regions 25A, 25B extend.

In greater detail, the etching operations shown in FIGS. 31 and 32 leadto formation of a first additional trench T1′ and a second additionaltrench T2′, which are arranged symmetrically with respect to the planeof symmetry SH and extend on opposite sides of the read/write head 404.Furthermore, to a first approximation, the first and second additionaltrenches T1′ and T2′ have a uniform depth such that, as explainedpreviously, the first and second additional trenches T1′ and T2′traverse the second parts 25A″, 25B″ of the first and second innercoating regions 25A, 25B, and therefore communicate with the first andsecond cavities 22, 24, respectively, but do not traverse the firstparts 25A′, 25B′ of the first and second inner coating regions 25A, 25B.

As regards the vertical extension of the first and second additionaltrenches T1′ and T2′, the presence of the oxidized regions formed by thefirst parts 25A′, 25B′ and the second parts 25A″, 25B″ of the first andsecond inner coating regions 25A, 25B enables precise control of theextension in depth of the etch, for example using the second parts 25A″,25B″ of the first and second inner coating regions 25A, 25B as etch-stoppoints.

Given the symmetry, in what follows the first additional trench T1′ isdescribed, except where otherwise specified. Portions of the secondadditional trench T2′ that are the same as portions of the firstadditional trench T1′ are designated by the same references, but “1” isreplaced by “2”. In addition, the ensuing description refers to FIGS.32-38. As regards FIGS. 33-38, it is here assumed, for simplicity ofrepresentation, that the first and second inner coating regions 25A,25B, the conductive region 19, the coupling layer 211, the gluing region305, and the first and second top electrode regions 36, 38 are absent.Moreover, it is assumed that the first and second additional trenchesT1′, T2′ extend as far as the bottom walls P₁′, P₂′ of the first andsecond cavities 22, 24. In addition, it is assumed that the first outercoating region 25C and the second dielectric layer 207 form a regionR_(ox), referred to in what follows as the thin region R_(ox). It islikewise assumed that the first and second coating layers 208, 209 arenegligible and that the conductive paths CP are absent. Consequently,the preliminary deformable region 240′ extends as far as the thin regionR_(ox).

Once again with reference to FIGS. 33-38, the aforementioned contourlines 122, 124 present in said figures are projected on the top surfaceof the top structure 400. In addition, further contour lines are shown,which are designated by 132 and 134 and represent (approximately) thecontour of the first and second piezoelectric regions 32, 34,respectively. Likewise denoted by I* and I** are the lines thatrepresent the projections of the inner side walls of the first andsecond trenches T1, T2, respectively, whereas denoted by 1302 is thecontour line of the housing cavity 302. Moreover, denoted by W_(cavity),W_(membrane), and W_(ox), respectively, are the projections of theheights of the first and second cavities 22, 24, of the membrane regionM, and of the thin region R_(ox). Denoted by I_(bot_302) is a sideprojection of the height of the bottom base of the housing cavity 302.

All this having been said, the first additional trench T1′ comprises afirst transverse portion TT1′ and a second transverse portion TT1″ and alongitudinal portion TL1′, which, as mentioned previously, extend, to afirst approximation, as far as a same depth and have a parallelepipedalshape. Furthermore, the first and second transverse portions TT1′, TT1″extend parallel to the axis B and are connected by the longitudinalportion TL1′, which is interposed between them and extends parallel tothe axis A. For simplicity of representation, the portions of the firstadditional trench T1′ are shown in FIGS. 32, 34, and 35; the portions ofthe second additional trench T2′ are shown in FIGS. 32 and 34.

In greater detail, the first transverse portion TT1′ extends in aportion of the main body 402 and in an underlying portion of thesemiconductor body 201 (as well as through a corresponding portion ofthe coupling layer 211, which in what follows will generally no longerbe mentioned, except where otherwise specified), which are laterallystaggered with respect to the housing cavity 302. Moreover, the firsttransverse portion TT1′ extends in a portion of the main body 402 and inan underlying portion of the semiconductor body 201 that overlie thesecond trench T2 so that the first transverse portion TT1′ of the firstadditional trench TT1 communicates with the underlying second trench T2.In addition, the first transverse portion TT1′ extends through a portionof the main body 402 and in an underlying portion of the semiconductorbody 201 that overlie the first cavity 22 and a part of the intermediatesemiconductor region 23 adjacent to the first cavity 22, as well asthrough an underlying portion (not illustrated) of the second part 25A″of the first inner coating region 25A and through said adjacent part ofthe intermediate semiconductor region 23. In particular, as shown inFIG. 32, and without this implying any loss of generality, the firsttransverse portion TT1′ has a shape (approximately) symmetrical withrespect to a plane (not shown) parallel to the plane BC and coplanarwith the side wall of the first cavity 22 parallel to the plane BC closeto the plane of symmetry SH. In this regard, albeit not shown, variantsare possible where the first and second transverse portions TT1′, TT2′are close to the plane of symmetry SH to such a point as not tocommunicate with the first and second cavities 22, 24.

The longitudinal portion TL1′ of the first additional trench T1′ has itsaxis parallel to the plane CA and extends through a portion of the mainbody 402 and an underlying portion of the semiconductor body 201 thatoverlie the first cavity 22, as well as in an underlying portion of thesecond part 25A″ of the first inner coating region 25A. Without thisimplying any loss of generality, the longitudinal portion TL1′ extendsparallel to the axis A so that part of the longitudinal portion TL1′overlies, at a distance, part of the first piezoelectric region 32.

In practice, the longitudinal portion TL1′ gives out into the firstcavity 22.

A first part of the second transverse portion TT1″ connects up to thelongitudinal portion TL1′ and extends in a portion of the main body 402and in an underlying portion of the semiconductor body 201 that overliethe first cavity 22, as well as through an underlying portion of thesecond part 25A″ of the first inner coating region 25A so as to face outinto the first cavity 22.

A second part of the second transverse portion TT1″ extends in a portionof the main body 402 and in an underlying portion of the semiconductorbody 201 that overlie the first trench T1 so that the second part of thesecond transverse portion TT1″ communicates with the underlying firsttrench T1.

Finally, a third part of the second transverse portion TT1″ extends in aportion of the main body 402 and in an underlying portion of thesemiconductor body 201, which are laterally staggered with respect tothe housing cavity 302 and overlie the preliminary deformable region240′. In this way, the third part of the second transverse portion TT1″exposes a corresponding part of the preliminary deformable region 240′.

In other words, the first and second parts of the second transverseportion TT1″ of the first additional trench T1′ both face out into thefirst cavity 22. Furthermore, the first part of the second transverseportion TT1″ is laterally staggered with respect to the first trench T1,whereas the second part of the second transverse portion TT1″ isarranged above the first trench T1. The third part of the secondtransverse portion TT1″ is delimited, underneath, by the preliminarydeformable region 240′.

In practice, the second transverse portion TT1″ and the longitudinalportion TL1′ of the first additional trench T1′ extend through portionsof the body 402 so as to delimit the read/write head 404 laterally.

As mentioned previously, to the second additional trench T2′, and inparticular to the arrangement of the latter with respect to the secondcavity 24, the housing cavity 302, the second piezoelectric region 34,and the preliminary deformable region 240′, there applies what has beensaid as regards the first additional trench T1′, and in particular asregards the arrangement of the first additional trench T1′ with respectto the first cavity 22, the housing cavity 302, the first piezoelectricregion 32, and the preliminary deformable region 240′.

As may be seen in FIGS. 31 and 36, the second transverse portions TT1″,TT2″ of the first and second additional trenches T1′, T2′ laterallydelimit a portion (designated by 1023) of the semiconductor body 201,which overlies the intermediate semiconductor region 23 and underliesthe read/write head 404; in what follows, said portion of thesemiconductor body is referred to as the mobile region 1023.

In addition, the first transverse portions TT1′, TT2′ of the first andsecond additional trenches T1′, T2′ laterally delimit a bridge structure999, which is formed by a portion of the main body 402 adjacent to theread/write head 404 and by an underlying portion of the semiconductorbody 201, adjacent to the mobile region 1023. A first end of the bridgestructure 999 is constrained to a fixed body, which is formed by thesemiconductor body 201 and by the main body 402 and is fixed withrespect to the supporting body 300 of the second wafer 299. A second endof the bridge structure 999 is fixed with respect to a first end of theread/write head 404 and to a first end of the underlying mobile region1023, which overlies the intermediate semiconductor region 23, andtherefore overlies a central portion M_(c) of the membrane region M,which in turn is suspended over the housing cavity 302. The read/writehead 404 is therefore fixed to the central portion M_(c) of the membraneregion M, which is interposed between the first and second membranes M′,M″, i.e., between two peripheral portions of the membrane region M, towhich the first and second piezoelectric regions 32, 34 are respectivelycoupled.

Following upon dicing operations that will be described hereinafter, asecond end of the read/write head 404, laterally staggered with respectto the first end, overlies a second end of the mobile region 1023, whichoverlies the first trench T1, extends laterally until it faces out overthe side surface Peat, and is constrained to the fixed body through acompliant region, represented by the deformable region 240. The firstand second ends of the read/write head 404 are laterally staggered in adirection parallel to the axis B. Each one of the first and secondmembranes M′, M″ has in turn a first end, fixed to the semiconductorbody 201, and a second end, which is laterally staggered with respect tothe first end in a direction parallel to the axis A and is fixed to thecentral portion M_(c) of the membrane region M.

Once again with reference to the manufacturing process, the assemblyformed by the first and second wafers 200, 299 and by the top structure400 is subjected to a process of singulation, which envisages carryingout dicing operations so as to form sub-assemblies that each include acorresponding actuator device 20 and a corresponding read/write head404. These dicing operations include execution of a cut along a cuttingline CL (represented in FIG. 32) parallel to the axis A and passingthrough the preliminary deformable region 240′. The remaining portion ofthe preliminary deformable region 240′ forms the deformable region 240.

Albeit not represented any further, following upon the dicingoperations, the remaining portions of the second dielectric layer 207and of the first and second coating layers 208, 209 form, respectively,the second, third, and fourth outer coating regions 27, 28, 29. Inaddition, the remaining portions of the top surface S_(top) and bottomsurface S_(bot) form, respectively, the first and second surfaces S₁,S₂.

In use, the present Applicant has noted how it is possible to control involtage the first and second piezoelectric regions 32, 34 so as todeform the membrane region M and cause, to a first approximation, aconsequent translation, parallel to the axis A, of the mobile region1023, and therefore also of the read/write head 404, fixed with respectto the latter. An example of said movement is shown in FIG. 39.

In detail, in FIG. 39 designated by 1100 is a mobile body formed by theread/write head 404 and by the mobile region 1023 (as well as by theportion of coupling layer 211 interposed between them), which has theshape of a parallelepiped with dimensions of, for example, 50 μm, 150μm, and 200 μm along the axes C, B, and A, respectively. Following uponapplication of a voltage of approximately 30 V to one of the first andsecond piezoelectric regions 32, 34 and upon consequent deformation ofthe portion of membrane region M that overlies the piezoelectric regionto which this voltage is applied (i.e., alternatively the first membraneM′ or the second membrane M″), the mobile body 1100 undergoes, to afirst approximation, a rototranslation. This rototranslation includes atranslation (designated by DT) parallel to the axis A, in the region ofsome thirty nanometers. Translation of the mobile body 1100 parallel tothe axis C is, to a first approximation, negligible, since it is in theregion of a few tens of nanometers. By changing the piezoelectric regionto which the voltage is applied, the direction of the translation DT isreversed. In particular, translation of the mobile body 1100 occurs in adirection of the piezoelectric region subjected to voltage, i.e., todeformation.

Rototranslation of the mobile body 1100 entails a deformation of thedeformable region 240, the compliance of which does not limit, to afirst approximation, the degree of rototranslation.

In practice, following upon the operations of singulation, each actuatordevice 20 forms, together with the corresponding read/write head 404, aMEMS (MicroElectroMechanical System) read/write device 1500, which islaterally delimited by the aforementioned side surface P_(ext).Furthermore, even though variants are possible in which the deformableregion 240 is absent (in other words, variants in which the recess 215is not filled by the preliminary deformable region 240′), the presenceof the deformable region 240 limits the number of openings of the MEMSread/write device 1500 that face out over the side surface P_(ext) justto the portions of the first and second additional trenches T1′, T2′that overlie the deformable region 240, which may have a reduced widthalong the axis A (for example, comprised between 0.5 μm and 2 μm). Inthis way, there is a reduction in the intensity of the turbulentaerodynamic forces to which the mobile body 1100 is subjected during itsrelative motion with respect to the disk 2, and the spurious movementsof the mobile body 1100, induced by said aerodynamic forces, aretherefore reduced. In this regard, in use it is precisely the sidesurface P_(ext) that faces the disk 2.

As may be seen in FIG. 40, moreover possible are variants, in which thenumber and shape of the bridge structures 999 are different from whathas been described. For instance, in the embodiment shown in FIG. 40,the first end of the read/write head 404 is fixed to two bridgestructures 999 that are the same as one another and laterally staggeredalong the axis A.

As shown in FIG. 41, it is moreover possible for the system ofconstraint of the first end of the read/write head 404 to be differentfrom what has been described and to include, for example, a pair ofsprings 1001, which are of alumina and are arranged, respectively,within the first and second additional trenches T1′, T2′. In particular,each spring 1001 is fixed between a corresponding portion of theread/write head 404 and a corresponding portion of the main body 402 ofthe top structure 400. The springs 1001 enable reduction of the depth ofthe notches parallel to the axis B.

A variant of the manufacturing process is described with reference toFIG. 42 and the subsequent figures. Also in this case, the descriptionis limited to a single actuator device 20 and to the portions coupledthereto.

In detail, as shown in FIG. 42, the second wafer, here designated by599, is initially provided. The base surface of the second wafer 599 ishere designated by 604 and is plane and without the housing cavity 302;moreover, the supporting body of the second wafer 599 is designated by600. In addition, the second wafer 599 may be of AlTiC or a materialdifferent from AlTiC; for example, the second wafer 599 may be of asemiconductor (e.g., silicon).

Formed on the base surface 604 is an intermediate dielectric regionR′_(ox), formed on which are the first and second piezoelectric regions32, 34, as well as, even though not shown, the conductive region 19 andthe first and second top electrode regions 36, 38. Moreover, as may beseen in FIG. 43, a top dielectric region R_(top) is formed on theexposed portions of the intermediate dielectric region R′_(ox) and onthe first and second piezoelectric regions 32, 34 (more precisely, onthe first and second top electrode regions 36, 38, not shown in FIG.43). Albeit not illustrated, the top dielectric region R_(top) may beformed, in turn, by a USG oxide layer and by an overlyingsilicon-nitride layer.

Next, as represented once again in FIG. 43, formed on the second wafer599, and in particular on the top dielectric region R_(top), is the topstructure 400, which includes the main body 402 and the read/write head404 (including the corresponding coil 405) and is once again delimitedon top by the surface to be etched S_(etch).

Next, as shown in FIG. 44, a process of etching the top structure 400 iscarried out so as to selectively remove, starting from the surface to beetched Sewn, portions of the main body 402 that overlie the first andsecond cavities 32, 34, respectively. In this way, a first recess 622and a second recess 624 are formed, which have approximately afrustopyramidal shape, with the minor base that overlies respectively,at a distance, the first and second piezoelectric regions 32, 34. Thisetching operation is of a time-based type. Consequently, the bottoms ofthe first and second recesses 622, 624 are formed, respectively, by afirst residual portion 642 and a second residual portion 644 of the mainbody 402, which coat corresponding portions if the top dielectric regionR_(top) and overlie the first and second piezoelectric regions 32, 34,respectively. Albeit not illustrated, variants are in any case possible,in which etching is carried out so as that the top dielectric regionR_(top) functions as etch stop. In this case, the bottoms of the firstand second recesses 622, 624 are formed, respectively, by a firstportion and a second portion of the top dielectric region R_(top), whichoverlie the first and second piezoelectric regions 32, 34, respectively.

The first and second recesses 622, 624 are closed laterally andlaterally delimit the read/write head 404, which is thus interposed inbetween.

Next, an operation of singulation of the assembly formed by the secondwafer 599 and the top structure 400 is carried out in a per se knownmanner, following upon which the MEMS read/write device 2500 is formed.This MEMS read/write device 2500 is shown in FIG. 45, where forsimplicity the top dielectric region R_(top), the conductive region 19,and the first and second top electrode regions 36, 38 are notrepresented.

In detail, the cut is so that the plane defined by the side surfaceP_(ext) traverses the first and second recesses 622, 624, which thusbecome open not only at the top but also on one side. Moreover, withoutthis implying any loss of generality, the cut passes through the firstand second residual portions 642, 644 of the main body 402. In addition,the first and second piezoelectric regions 32, 34 are at a distance fromthe side surface P_(ext) comprised, for example, between 5 μm and 10 μm.In practice, following upon the dicing operation, the first and secondrecesses 622, 624 face out over the side surface P_(ext).

Next, as illustrated in FIGS. 46 and 47, an etch is carried out startingfrom the side surface P_(ext) so as to selectively remove portions ofthe supporting body 600 of the second wafer 599 that extend underneaththe intermediate dielectric region R′_(ox) in order to form a pair oftrenches, referred to in what follows as first and second side trenchesLT1, LT2, respectively.

The first and second side trenches LT1, LT2 are the same as one anotherand symmetrical with respect to the plane of symmetry SH. Given thesymmetry, in what follows just the first side trench LT1 is described,except where otherwise specified. Portions of the second side trench LT2that are the same as portions of the first side trench LT2 and aredesignated by the same references, but with the “1” replaced by a “2”.

In detail, the first side trench LT1 comprises a longitudinal portionLTL1 and a vertical portion LTV1, which have, to a first approximation,a parallelepipedal shape and have a same extension in a directionparallel to the axis B.

The first piezoelectric region 32 extends entirely over the longitudinalportion LTL1, which moreover extends so as to be adjacent to theintermediate dielectric region R′_(ox). In other words, as may be seenin FIG. 46, the longitudinal portion LTL1 is delimited at the top and atthe bottom by a corresponding portion of the intermediate dielectricregion R′_(ox) and a corresponding portion of the supporting body 600 ofthe second wafer 599, respectively. However possible are embodiment,where present between the longitudinal portion LTL1 and the intermediatedielectric region R′_(ox) is a residual portion of supporting body 600.

The vertical portion TLV1 connects up to the longitudinal portion LTL1.Furthermore, along the axis C, the vertical portion TLV1 has a lengthgreater than the length of the longitudinal portion LTL1; for instance,along the axis C, the vertical portion TLV1 has a length, for example,of between 100 μm and 500 μm, whereas the longitudinal portion LTL1 hasa length of between 1 μm and 3 μm.

In side view, the vertical portion TLV1 and the longitudinal portionLTL1 are arranged at 90°, i.e., to form an L, and with vertical portionTLV1 facing the plane of symmetry SH.

In greater detail, the vertical portion TLV1 is laterally staggered withrespect to the first piezoelectric region 32 and is arranged underneaththe read/write head 404.

In practice, the vertical portions LTV1, LTV2 of the first and secondside trenches LT1, LT2 laterally delimit a part of the supporting body600 that forms a supporting structure 1999, which has a parallelepipedalshape. This parallelepipedal shape is free on three sides, whereas onthe fourth side and on the bottom base it is fixed to the remaining partof the supporting body 600. The read/write head 404 is fixed to the topbase of the parallelepipedal shape, as described in greater detailhereinafter.

The supporting structure 1999 has a symmetrical shape with respect tothe plane of symmetry SH. The first and second piezoelectric regions 32,34, as also the first and second recesses 622, 624, extend on oppositesides with respect to the supporting structure 1999, whereas theread/write head 404 is vertically aligned with respect to the latter.

For practical purposes, the first and second residual portions 642, 644form, together with underlying portions of the intermediate dielectricregion R′_(ox) and of the top dielectric region R_(top), the first andsecond membranes, here denoted by M* and M** (FIG. 46), which face outover the side surface P_(ext). Moreover, the first and second sidetrenches LT1, LT2 form corresponding cavities open laterally, betweenwhich the supporting structure 1999 extends. These cavities are closedat the top by a portion of the intermediate dielectric region R′_(ox),which forms, together with the first and second residual portions 642,644, the membrane region (designated once again by M in FIG. 46) andcarries the first and second piezoelectric regions 32, 34, which aretherefore coupled to corresponding peripheral portions of the membraneregion M. Said portion of the intermediate dielectric region R′_(ox)also carries the read/write head 404.

In greater detail, the read/write head 404 is fixed with respect to acentral portion (designated once again by M_(c) in FIG. 46) of themembrane region M, which is formed, on one side, in the intermediatedielectric region R′_(ox), is interposed between the peripheral portionsof the membrane region M, and is moreover fixed to the underlyingsupporting structure 1999. In addition, whereas a first end of theread/write head 404 faces out over the side surface P_(ext) and istherefore free, a second end of the read/write head 404, opposite to thefirst end and aligned to the latter in a direction parallel to the axisB, is fixed to the main body 402 of the top structure 400.

As may be seen in FIG. 48, it is found that, by applying in turns avoltage to the first piezoelectric region 32 and to second piezoelectricregion 32, 34, and thus causing deformation of the piezoelectric regionto which the voltage is applied, there is induced, to a firstapproximation, a translation of the read/write head 404 (and of thesupporting structure 1999) in a direction parallel to the axis A,towards the deformed piezoelectric region. The characteristics, and inparticular the degree, of the above movement are, to a firstapproximation, similar to the ones described with reference to FIG. 39.

Also in the embodiment illustrated in FIG. 46, each one of the first andsecond membranes M*, M** has a first end, which is fixed to the mainbody 402 and to the supporting body 600, and a second end, which islaterally staggered with respect to the first end in a directionparallel to the axis A and is fixed to the central portion M_(c) of themembrane region M.

In practice, the actuator device and the read/write head form aread/write device, which affords advantages that emerge clearly from theforegoing description. In particular, it is possible to translate theread/write head with respect to the supporting body obtained startingfrom the second wafer, which functions as slider. Moreover, the degreeof said translation is sensibly higher than what can be obtained withthe solutions according to the prior art.

Finally, it is clear that modifications and variations may be made towhat has been described and illustrated herein, without therebydeparting from the scope of the present disclosure.

For instance, the alignments may be different from what has beendescribed, for example so as to take into account possible tolerances ofthe manufacturing process. In particular, the alignments between thefirst and second cavities 22, 24 and the first and second trenches T1,T2 may vary, as well as the alignments with respect to the housingcavity. Likewise, the shape and arrangement of the first and secondadditional trenches T1, T2′ may vary.

It is moreover possible for the first and second cavities 22, 24 to havewalls without oxide coating, in which case, however, control of thedepth of the first and second additional trenches T1, T2′ may be moreproblematical.

The number and shape of the piezoelectric regions may vary with respectto what has been described.

As mentioned previously, the materials may be different from the onesdescribed and/or regions may be present additional to the onesdescribed. For instance, metal paths may extend within the main body 402of the top structure 400.

The first and second additional trenches T1′, T2′ can terminate,respectively, on corresponding portions of the second parts 25A″, 25B″of the first and second inner coating regions 25A, 25B, withouttraversing them. In this case, in fact, the portions of the second parts25A″, 25B″ that would delimit the bottoms of the first and secondadditional trenches T1′, T2′ would be thin to such a point as to undergofailure at the very first actuation.

The various embodiments described above can be combined to providefurther embodiments. These and other changes can be made to theembodiments in light of the above-detailed description. In general, inthe following claims, the terms used should not be construed to limitthe claims to the specific embodiments disclosed in the specificationand the claims, but should be construed to include all possibleembodiments along with the full scope of equivalents to which suchclaims are entitled. Accordingly, the claims are not limited by thedisclosure.

1. A read/write device for a hard-disk memory system, comprising: afixed structure; a membrane region including first and second membranes,which are coupled to the fixed structure, and a central portioninterposed between the first and second membranes; first and secondpiezoelectric actuators, which are mechanically coupled to the first andthe second membranes, respectively; and a read/write head, which isfixed to the central portion of the membrane region, wherein the firstand the second piezoelectric actuators are configured to causecorresponding deformations in the first and second membranes,respectively, the deformations in the first and second membranes causecorresponding movements of the read/write head with respect to the fixedstructure.
 2. The read/write device according to claim 1, wherein theread/write device is laterally delimited by a side surface, theread/write head overlies the central portion of the membrane region andhas a first end, which is fixed to the fixed structure, and a secondend, which is laterally staggered with respect to the first end andextends over the side surface.
 3. The read/write device according toclaim 2, wherein the first and second ends of the read/write head arearranged in a first direction; and wherein each one of the first andsecond membranes has a first end, which is fixed to the fixed structure,and a second end, which is fixed to the central portion of the membraneregion, the first and second ends of each one of the first and secondmembranes being arranged along a second direction, transverse to thefirst direction.
 4. The read/write device according to claim 3, whereinthe fixed structure delimits a main cavity, and the membrane region issuspended over the main cavity; wherein the read/write device furtherincludes a semiconductor body that forms part of the fixed structure andthe membrane region, and houses a first and a second secondary cavity;wherein the first and second piezoelectric actuators are arranged on afirst side of the membrane region, facing the main cavity; wherein thefirst and second secondary cavities are arranged on a second side of themembrane region and above the first and second piezoelectric actuators,respectively, and laterally delimit an intermediate portion of thesemiconductor body, which is interposed between the first and secondsecondary cavities and overlies the central portion of the membraneregion; wherein the semiconductor body includes a mobile portion, whichoverlies the intermediate portion; and wherein the read/write head isfixed to the mobile portion of the semiconductor body.
 5. The read/writedevice according to claim 4, further comprising: a top structure thatincludes a material different from a material of the semiconductor body,overlies the semiconductor body, and forms the read/write head; firstand second top trenches that extend downwards, through the top structureand part of the semiconductor body, up to the first and the secondsecondary cavities, respectively, so as to delimit laterally: a mobilegroup, which includes the read/write head and the mobile portion of thesemiconductor body; and a connection structure, which includes portionsof the top structure and of the semiconductor body laterally staggeredwith respect to the read/write head and to the mobile portion,respectively, the connection structure having a respective first end anda respective second end, which are fixed, respectively, to the fixedstructure and to the mobile group.
 6. The read/write device according toclaim 5, further comprising: first and second bottom trenches, whichextend upwards, through the semiconductor body, until the first andsecond bottom trenches are fluidically coupled with the first and thesecond secondary cavities, wherein the first and second bottom trenchesextend over the main cavity and laterally delimit the membrane region.7. The read/write device according to claim 6, wherein the mobile regionof the semiconductor body extends laterally so as to overlie a part ofthe first bottom trench and extend over the side surface, underneath thesecond end of the read/write head; wherein the read/write device furtherincudes a deformable region that is interposed between the first bottomtrench and the side surface, and extends over the side surface,underneath the mobile region of the semiconductor body.
 8. Theread/write device according to claim 7, wherein the first and second toptrenches extend over the side surface and are in part delimited by thedeformable region; and wherein the deformable region prevents the firstbottom trench from accessing the side surface.
 9. The read/write deviceaccording to claim 7, wherein the deformable region is of a siliconepolymer.
 10. The read/write device according to claim 4, wherein thefixed structure includes a bottom body; and wherein the semiconductorbody is interposed between the top structure and the bottom body; andwherein the main cavity extends in the bottom body.
 11. The read/writedevice according to claim 10, wherein the top structure is made at leastin part of alumina.
 12. The read/write device according to claim 10,wherein the bottom body is of an AlTiC alloy.
 13. The read/write deviceaccording to claim 2, comprising: a bottom body and a top structure,which extends on the bottom body and forms the read/write head; whereinparts of the bottom body and of the top structure form the fixedstructure; wherein the bottom body houses first and second secondarycavitites, extending over which are the first and second membranes,respectively; wherein the first and second secondary cavities laterallydelimit a supporting portion of the bottom body, which is interposedbetween the first and second secondary cavities; wherein the centralportion of the membrane region overlies the supporting portion of thebottom body; and wherein the first and second secondary cavities areopen laterally and extend over the side surface.
 14. The read/writedevice according to claim 13, further comprising: first and secondrecesses that extend through the top structure, overlie the first andsecond membranes, respectively, and laterally delimit the read/writehead, which is interposed between the first and second recesses; whereinthe first piezoelectric actuator is interposed between the first recessand the first secondary cavity; and wherein the second piezoelectricactuator is interposed between the second recess and the secondsecondary cavity.
 15. The read/write device according to claim 14,wherein the top structure is made at least in part of alumina.
 16. Theread/write device according to claim 13, wherein the bottom body is ofAlTiC.
 17. A memory system, comprising: a magnetic disk with a pluralityof magnetic tracks configured to store data; and a read/write deviceincluding: a fixed structure; a membrane region including first andsecond membranes, which are coupled to the fixed structure, and acentral portion, interposed between the first and second membranes;first and second piezoelectric actuators, which are mechanically coupledto the first and the second membranes, respectively; and a read/writehead, which is fixed to the central portion of the membrane region,wherein the first and the second piezoelectric actuators are configuredto cause corresponding deformations in the first and second membranes,respectively, the deformations in the first and second membranes causecorresponding movements of the read/write head with respect to the fixedstructure, the read/write device is laterally delimited by a sidesurface, the read/write head overlies the central portion of themembrane region and has a first end, which is fixed to the fixedstructure, and a second end, which is laterally staggered with respectto the first end and extends over the side surface, the side surfaceextends over the magnetic disk.
 18. A process for manufacturing aread/write device for a hard-disk memory system, the process comprising:forming a fixed structure; forming a membrane region including first andsecond membranes, which are coupled to the fixed structure, and acentral portion interposed between the first and second membranes;forming first and second piezoelectric actuators, which are mechanicallycoupled to the first and second membranes, respectively; and forming aread/write head, which is fixed to the central portion of the membraneregion, wherein the forming of the first and second piezoelectricactuators includes forming the first and second piezoelectric actuatorsso that the first and second piezoelectric actuators are configured tocause corresponding deformations of the first and second membranes,respectively, the deformations in the first and second membranes causecorresponding movements of the read/write head with respect to the fixedstructure.
 19. The process according to claim 18, further comprising:forming a side surface that laterally delimits the read/write device,wherein the forming of the read/write head includes forming theread/write head so that the read/write head overlies the central portionof the membrane region and has a first end, which is fixed to the fixedstructure, and a second end, which is laterally staggered with respectto the first end and extends over the side surface.
 20. The processaccording to claim 19, wherein the first and second ends of theread/write head are arranged in a first direction; and wherein each oneof the first and second membranes has a first end, which is fixed to thefixed structure, and a second end, which is fixed to the central portionof the membrane region, the first and second ends of each one of thefirst and second membranes being arranged in a second direction,transverse with respect to the first direction.
 21. The processaccording to claim 20, further comprising: in a semiconductor body of anintermediate wafer that is delimited by a front surface, forming firstand second secondary cavities of a buried type, which are laterallystaggered so that extending between the front surface and the first andsecond secondary cavities is a front semiconductor region, the first andsecond secondary cavities laterally delimiting an intermediate portionof the semiconductor body, which is interposed between the first andsecond secondary cavities and underlies the central portion of themembrane region; forming, through the front semiconductor region, firstand second holes that are fluidically coupled with the first and secondsecondary cavities, respectively; forming a first dielectric layer thatextends through the first and second holes and is on the walls of thefirst and second secondary cavities internally; forming, on the frontsurface, the first and second piezoelectric actuators, so that the firstand second piezoelectric actuators overlie the first and secondsecondary cavities, respectively; forming a recess, which extendsthrough the semiconductor body and is laterally staggered with respectto the first and second secondary cavities; forming a preliminarydeformable region within the recess; and selectively removing portionsof the front semiconductor region so as to form first and second bottomtrenches, which extend on opposite sides of the first and secondpiezoelectric actuators, each one of the first and second bottomtrenches extending downwards until the first and second bottom trenchesare fluidically coupled with the first and the second secondarycavities, the first and second bottom trenches laterally delimiting themembrane region, the first bottom trench being interposed between themembrane region and the preliminary deformable region.
 22. The processaccording to claim 21, wherein each one of the first and secondsecondary cavities is delimited by a respective bottom wall, which iscoated with a corresponding portion of the first dielectric layer, whichis delimited at the top by a respective top surface; and wherein theforming of the recess includes forming the recess so that the recessextends up to a depth at least equal to a depth to which the topsurfaces of the portions of the first dielectric layer extend.
 23. Theprocess according to claim 21, further comprising: coupling theintermediate wafer to a bottom wafer, which includes a supporting bodythat delimits a main cavity, the coupling including arranging theintermediate wafer so that the membrane region is interposed between thefirst and second secondary cavities and the main cavity; forming a topstructure including the read/write head on the intermediate wafer, andwherein forming of the top structure includes forming the read/writehead on a mobile portion of the semiconductor body, which overlies theintermediate portion of the semiconductor body; selectively removingportions of the top structure and underlying portions of thesemiconductor body so as to form first and second top trenches, whichextend through the top structure and part of the semiconductor body,until the first and second trenches are fluidically coupled with thefirst and second secondary cavities, respectively, so as to delimitlaterally a mobile group, wherein the mobile group includes: theread/write head and the mobile portion of the semiconductor body, and aconnection structure that includes portions of the top structure and ofthe semiconductor body laterally staggered with respect to theread/write head and to the mobile portion, respectively, the connectionstructure having a respective first end and a respective second end,which are fixed, respectively, to the fixed structure and to the mobilegroup, the fixed structure being formed by parts of the top structure ofthe semiconductor body and of the supporting body.
 24. The processaccording to claim 23, wherein the first and second top trenches extendlaterally so as to overlie and expose corresponding parts of thepreliminary deformable region.
 25. The process according to claim 24,wherein the first and second top trenches extend laterally so that eachoverlies both the first and the second bottom trenches.
 26. The processaccording to claim 23, wherein the forming of the first and second toptrenches includes forming the first and second top trenches so that theyextend at least as far as corresponding portions of the first dielectriclayer that coat the bottom walls of the first and second secondarycavities.
 27. The process according to claim 26, further comprising:cutting the top structure, the intermediate wafer, and the bottom waferalong a cutting line that passes through the preliminary deformableregion.
 28. The process according to claim 19, further comprising:forming the first and second piezoelectric actuators on a supportingbody of a bottom wafer; forming a top structure which includes theread/write head on the bottom wafer; selectively removing portions ofthe top structure so as to form first and second recesses, which arearranged on opposite sides of the read/write head and overlie the firstand second piezoelectric actuators, respectively; selectively removingportions of the supporting body arranged underneath the first and secondpiezoelectric actuators, respectively, so as to form first and secondbottom trenches, which delimit the first and second membranes and areopen laterally so as to extend over the side surface, wherein the firstand second bottom trenches laterally delimit a supporting portion of thebottom body, which is interposed between the first and second secondarycavities, the read/write head being fixed to the supporting portion ofthe bottom body.
 29. The process according to claim 28, furthercomprising: after forming the first and second recesses and beforeforming the first and second bottom trenches, cutting the bottom waferand the top structure along a cutting line that traverses the first andsecond recesses so as to open the first and second recesses laterallyand form the side surface.